KR100193690B1 - White porous polyester film and its manufacturing method - Google Patents

Abstract

The present invention discloses a white porous polyester film including a polyester resin, a polyolefin resin and a graft copolymer of succinic anhydride or maleic anhydride in polypropylene as a compatibilizer capable of improving compatibility thereof. Due to the compatibilizer, the polyolefin is properly distributed in the polyester resin to form pores, thereby obtaining a light white paper-like porous film. Such a white porous polyester film can be used in various fields such as calendars, advertising papers, high-quality wrapping papers, printing papers, wallpaper as a substitute for paper.

Description

White porous polyester film and its manufacturing method

The present invention relates to a polyester film and a method for producing the same, and in particular, to a white porous polyester film and a method for producing the same, which can be used as a substitute for paper because of its lightness, excellent texture, good thermal stability and printing characteristics.

White polyester film retains polyester's inherent properties in terms of mechanical properties, heat resistance and dimensional stability, and is excellent in light blocking, whiteness, and paper-like color, so it is suitable for calendars, advertisements, high-quality packaging, printing paper, wallpaper, etc. It has been used as a substitute, and polyolefin-based films containing a large amount of inorganic particles have also been used as packaging materials and printing materials as paper substitutes.

However, the white polyester film has the above-mentioned advantages, but has a disadvantage in that it is stiff and the touch is too smooth to texture compared to paper, and the polyolefin-based film used as a substitute for paper also has good texture. And disadvantages of poor thermal properties.

In order to overcome these disadvantages, a method has been developed that can exhibit a paper-like texture while maintaining the excellent properties of the polyester film, and can reduce the mass per unit area to about the weight of a polyolefin-based film.

As an example of such a method, Japanese Patent Application Laid-Open Nos. 62-243210 and Pyeong 2-206622 disclose methods for adding inorganic fine particles to polyester, and Japanese Patent Application Laid-Open No. 58-50625 discloses a method for adding polyester to polyester. A method of blending a foaming agent to reduce the weight is disclosed, and Japanese Patent Application Laid-Open No. 57-49648 improves the surface properties of a film by forming fine pores on the surface and inside of the film by blending and stretching a polyolefin resin in polyester. And lightening the film itself is disclosed.

When the polyolefin resin is mixed with the polyester resin and subjected to extrusion, molding, and stretching, fine pores are formed on the surface and inside of the film due to poor compatibility between the two resins. Therefore, using the above properties, the surface properties of the film can be improved and the weight can be realized. However, the polyolefin resin is used in combination with the polyester resin. However, the pores are limited and the pores themselves are uneven. There is a problem that the printing is uneven because there are many partially exposed or recessed parts. Therefore, in order to solve such a problem, the compatibility between the two resins needs to be maintained at an appropriate level.

In general, paper-like texture and surface characteristics can be changed very sensitively depending on the shape and distribution of pores present in the film.If the pore distribution is not designed correctly when forming the pores, the desired paper texture can not be obtained and the weight is reduced. It also adversely affects fairness. In fact, if the size of the pores present in the film is small, the specific gravity is high and heavy, while if the pores are too large, there is a problem in the processability due to breakage. Therefore, in order to obtain a film which is not insufficient for use as a paper substitute, matters concerning the distribution of pores in the film and the like must be appropriately designed.

Accordingly, an object of the present invention is to provide a white porous film having excellent whiteness and texture, and a method of manufacturing the same, because the size, shape, and distribution of pores present in the film are properly made.

In order to achieve the above object, in the present invention, in the white porous polyester film made of a polyester resin and a polyolefin resin, a resin obtained by graft copolymerization of succinic anhydride or maleic anhydride in polypropylene is used as a compatibilizer. It is provided with a white porous polyester film comprising 0.5 to 5% by weight based on the total amount of.

The density of the white porous polyester film is preferably 1.1 to 1.25 gr / cm ³ in terms of light weight.

Preferably, the content of the polyolefin-based resin is 5 to 35% by weight based on the total amount of the resin, the melt index is 1 to 25gr / min. In addition, the polyolefin resin is preferably polymerized or copolymerized from at least one monomer selected from ethylene, propylene, butene, pentene, hexene and octene.

The polyester resin is preferably at least one selected from polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), more preferably 0.005 to 0.5% by weight of the hindered phenol compound. In addition, preferably, the polyester resin contains 0.01 to 10% by weight of inorganic fine particles having a diameter of 0.01 to 10㎛. Such inorganic fine particles are preferably at least one compound selected from titanium dioxide, barium sulfate, calcium carbonate, silica, kaolin, talc and zeolite.

Another object of the present invention is to prepare a white porous polyester film of a polyester resin and a polyolefin resin, the polyester resin and polyolefin resin by mixing in a weight ratio of 95: 5 to 65:35 Forming a first mixed resin, adding 0.5 to 5 wt% of a compatibilizer made of a polymer having maleic anhydride and succinic anhydride graft copolymerized to polypropylene to form a second mixed resin; And melting and extruding the second mixed resin to form a film sheet and biaxially stretching the film sheet.

Preferably, the polyester resin includes a hindered phenolic compound and / or inorganic fine particles.

In the step of forming the film sheet, the average diameter of the polyolefin in the film sheet is preferably 5 µm or less, and the average number of polyolefins in the film sheet 1000 µm ² is preferably 50 or more.

In the biaxial stretching step, the stretching is preferably made of a draw ratio of 2 to 5 times in both the longitudinal and transverse directions.

Hereinafter, the manufacturing method of the white porous film of the present invention and the principle of the present invention will be described in detail.

First, a polyester-based resin is prepared, and the polyester-based resin used in the present invention is polyethylene terephthalate, polyethylene naphthalate or a mixture thereof, and a glycol having a main component of an acidic component and an alkylene glycol having an aromatic dicarboxylic acid as a main component. It is manufactured by polycondensing a component. At this time, the aromatic dicarboxylic acid is dimethyl terephthalic acid, terephthalic acid, isophthalic acid, dimethyl-2,5-naphthalenedicarboxylic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, diphenoxy ethane dicarboxylic acid, diphenyldicarboxylic acid, diphenyl ether dicarboxylic acid At least one selected from the group consisting of anthracenedicarboxylic acid and α, β-bis (2-chlorophenoxy) ethane-4,4-dicarboxylic acid. In addition, examples of the alkylene glycol include ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol and hexylene glycol.

The polyester resin of the present invention is prepared according to a conventional polyester synthesis method, 70% by weight or more is composed of a homopolyester of polyethylene terephthalate or polyethylene naphthalate as described above, copolymerization within a range of 30% by weight As a specific example of such copolymerization components, diols such as diethylene glycol, propylene glycol, neopentylene glycol, polyethylene glycol, p-xylene glycol, 1,4-cyclohexanedimethanol, and 5-sodium sulforezocin And polyfunctional dicarboxylic acids such as dicarboxylic acids such as adipic acid and 5-sodium sulfoisophthalic acid, trimethyl acid and pyromethyl acid.

In preparing the polyester resin of the present invention, a hindered phenol compound and an inorganic particle may be added.

The hindered phenolic compound acts as a radical chain inhibitor for the thermal oxidation of polyolefin, and is added at a ratio of 0.005 to 0.5% by weight relative to the polyester resin. If the added amount is less than 0.005% by weight, the effect of improving the heat resistance of the polyolefin is extremely minimal, and if it exceeds 0.5% by weight, the cost is increased without further improving the thermal stability effect. As a hindered phenol type compound, tetrakis 3, 5- di- t-butyl hydroxy phenyl propanoyl oxymethyl methane, an octadecyl 3, 3, 5- di- t- butyl- 4-hydroxyphenyl propanoate , At least one selected from the group consisting of 2-hydroxy-4-n-octacybenzophenone, 2,4-di-t-butylphenyl and 3,5-di-t-butyl-4-hydroxybenzoate One compound is used.

In addition, the inorganic fine particles are added to the polyester-based resin for the purpose of adjusting optical properties such as light transmittance or color, and control of friction coefficient, surface roughness and fine touch, the particle diameter is preferably in the range of 0.1 to 10㎛, The addition amount is 0.1 to 10 weight% with respect to polyester resin, Preferably it is 0.1 to 5 weight%. If the particle size is less than 0.1㎛ the effect on the optical properties and surface properties is insignificant, and when the particle size exceeds 10㎛ the surface roughness of the film is excessively increased to give a rough feeling. In addition, when the addition amount is less than 0.1% by weight, the effect of addition is insignificant, and when the addition amount is more than 10% by weight, the optical or surface properties are inferior to obtain a paper-like texture. As a result, the pressure increase is accelerated and the life of the filter is reduced, the production efficiency is lowered, the dispersibility is worsened, the fracture is increased, and the weight is also reduced. Examples of inorganic fine particles that can be used include titanium dioxide, barium sulfate, calcium carbonate, silica, kaolin, talc, zeolite and the like.

In addition, polycondensation catalysts, dispersants, electrostatic agents, crystallization accelerators, antiblocking agents and inorganic lubricants may be further added as additives in addition to the main components in the preparation of the polyester resin of the present invention. Typically, materials used for this purpose are used.

The polyolefin resin mixed with the polyester resin is preferably polymerized from at least one monomer of ethylene, propylene, butene, pentene, hexene and octene, and more particularly polymerized using propylene as a main component and other monomers as an auxiliary component. desirable. In addition, a melt index of 1 to 25 gr / min is effective for pore formation, and preferably 5 to 35% by weight based on the total amount of resin. When it is less than 5% by weight, the formation of pores is generally nonuniform and occupies the entire pores When the ratio is small, the film becomes stiff, and when it exceeds 35% by weight, the formation of pores is sufficient, but the heat resistance and mechanical properties of the polyolefin which is poor due to the increase in the heat resistance and mechanical properties of the resulting film is poor and the processability is also poor.

After mixing the polyester resin and the polyolefin resin, a compatibilizer is added to improve the compatibility between them and to give a papery texture. The addition ratio of the compatibilizer is preferably 0.5 to 5% by weight based on the total amount of the resin, and more preferably 1 to 3% by weight. If the addition ratio of the compatibilizer is less than 0.5% by weight, the effect of improving the compatibility is insignificant, and there is a limit in the formation of pores, and the pores themselves are uneven, so that the pores are partially exposed or recessed on the surface, resulting in poor printability. When the addition ratio of the compatibilizer exceeds 5% by weight, the polypropylene and the polyester are similar to the continuous phase form, so that little pores are generated.

That is, the compatibilizer used in the present invention serves to control the compatibility between the polyester resin and the polyolefin resin. In more detail, the addition of a compatibilizer results in a small and uniformly large amount of polyolefin resin in the polyester resin and a large contact area of the polyolefin in contact with the polyester resin, thereby increasing the total porosity and uniformly distributing the pores. . As a result, the resulting film has a lower density, resulting in lighter weight, increased flexibility of the film, and improved printability since the surface of the film is embossed.

As a compatibilizer having such a function, it is used in the present invention is a material in which polypropylene is graft copolymerized with maleic anhydride or succinic anhydride, and the polyester resin and the polyolefin resin are formed by the interaction of the polyester resin with maleic anhydride or succinic anhydride. The compatibility between them becomes high. The compatibilizer of the present invention is somewhat inferior in compatibility improvement effect, but relatively inexpensive to use a large amount can avoid the complexity of the process due to the addition of the compatibilizer. That is, in the case of a compatibilizer having high compatibility improvement effect, the desired density and flexibility can be secured even in a small amount, but the process becomes much more complicated for uniform compounding due to the use in a small amount. In the case of the compatibilizer of the present invention, it is possible to achieve uniform compounding even through a simple process and has an advantage of being inexpensive in terms of price.

As described above, when the polyester resin, the polyolefin resin, and the compatibilizer are mixed, a mixed resin is obtained. The mixed resin is dried, melted, and extruded in the same manner as in the conventional polyester manufacturing method to obtain a film. After the sheet is obtained, the sheet is stretched 2 to 5 times, preferably 3 to 4.5 times in the longitudinal and transverse directions, respectively. If the draw ratio is smaller than this, the formation of pores is poor, the density is high, the mechanical properties and the whiteness is also reduced, while the draw ratio is larger than this, the breakage of the film increases.

The dispersion state of the polyolefin resin in the mixed resin, especially the film sheet before stretching, has a significant influence on the properties of the film finally obtained. The dispersion state of the polyolefin resin can be known by observing a compounding chip or a sheet made after remelting with an electron microscope. That is, the dispersion state can be evaluated by measuring the average particle number and the number of the polyolefin resin dispersed in the sheet via an electron microscope. As a result, when the average diameter of the polyolefin particles is 5㎛ or less, the effect of improving the uniform dispersibility and film properties is apparent, and when the average number of polyolefins in 1000㎛ ² or more 50 or more, the decrease in density and the improvement in flexibility are apparent.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the scope of the present invention is not limited to the following Examples. Performance evaluation of the film produced in the following Examples was carried out in the following manner.

(1) the size and number of pores

The cross section was observed using an electron scanning microscope manufactured by Jeol, Japan, and measured using an image analyzer.

(2) Average particle diameter of inorganic fine particles

The slurry of the inorganic fine particles disperse | distributed to ethylene glycol was measured using the centrifugal particle size analyzer of Shimadzu Corporation, Japan, and is shown as a volume average particle diameter.

(3) apparent density

The density gradient tube consisting of carbon tetrachloride and n-heptane was kept at 25 ° C. and measured by the ups and downs method.

(4) breaking strength

Tensile strength of the film was measured according to ASTM D 882 using UTM of Instron, USA.

(5) Process stability

Relative evaluation was made by measuring the frequency of breakage of the film for 12 hours during the film forming process and the discharge state and chip cutting conditions under the same process / cooling conditions during the compounding process.

Compounding Fairness:

A: Both discharge / chip cutting condition is good, B: One of discharge / chip cutting condition is bad

C: Bad discharge / chip cutting

Production Process Fairness:

A: One break occurs, B: Two to three breaks occur, C: Four or more breaks occur

(6) texture and appearance

The surface appearance, color, glossiness, state of depression pores, size, uniformity, etc. are comprehensively evaluated to indicate good or bad.

Example 1

Dimethyl terephthalate and ethylene glycol were mixed in a 1: 2 equivalent ratio, and then a transesterification catalyst was added to the mixture to form bis-2-hydroxyethyl terephthalate as a monomer of polyethylene terephthalate. To this, 5% by weight of titanium dioxide having a cubic crystal structure with an average particle diameter of 0.5 µm, 0.2% by weight of tetrakis-3,5-di-t-butylhydroxyphenylpropanoyloxymethylmethane and a polycondensation catalyst were added. The polycondensation was completed to prepare a polyester resin having an intrinsic viscosity of 0.614 dl / gr. 90% by weight of the polyester resin and 10% by weight of the random polypropylene-ethylene copolymer having a melt index of 4.0 were mixed, and then 2% by weight of polypropylene-maleic anhydride (PP-MA) was added as a compatibilizer. A biaxially stretched polymer film having a thickness of 38 µm by making a mixed resin by a pounding method, drying, melting, and extruding according to a conventional polyester film manufacturing method to form a sheet, followed by stretching four times each of the longitudinal draw ratio and the transverse draw ratio. Was prepared. The film was evaluated for properties according to the method described above for this film, and the results are shown in Table 1 below.

As shown in Table 1, the film prepared in this example had excellent processability, good texture and appearance, and good breaking strength.

Example 2

In the same manner as in Example 1, but using dimethyl-2,5-naphthalenedicarboxylate instead of dimethylterephthalate to obtain a polyethylene naphthalate resin having an ultimate viscosity of 0.61 dl / gr, the same amount as in Example 1 Polyolefin was added, 1.5 wt% of a compatibilizer was added, and the same procedure as in Example 1 was carried out to obtain a biaxially stretched polymer film having a thickness of 38 μm. Various properties were evaluated in the same manner as described above for this film, and the results are shown in Table 1 below.

Examples 3-4

A polymer film was obtained in the same manner as in Example 1 except that the amount of the polyolefin and various additives was changed as shown in Table 1, and then the properties thereof were evaluated in the same manner. Table 1 shows.

As shown in Table 1, the distribution of pores is maintained at a desirable level as long as the addition amount of various additives is maintained in a limited range in the present invention, so that both the texture and appearance of the film are good, and the weight is made to some extent and fairness It can also be seen that excellent.

Comparative Example 1-6

The polymer film was obtained in the same manner as in Example 1 except that the amount of the polyolefin and various additives was changed as shown in Table 1, and then the properties thereof were evaluated in the same manner. Table 1 shows.

As can be seen from Table 1 below, unlike the case of the examples, when the amount of the various additives is out of the preferred range defined in the present invention, the obtained film was found to be poor in at least one or more of the various properties evaluated.

TABLE 1

Basic resin additive Olefin-Based Resin pore Fairness Physical properties of the final film Inorganic particles stabilizator Compatibilizer type content Average number Average diameter Compounding Production density Texture / Appearance Breaking strength No. - Kinds wt% wt% wt% Copolymerization wt% 1000 μm ² Μm - - g / cm ³ - kg / mm ² Example One PET TiO ₂ 8 0.05 2.0 PP 10 62 4.3 A A 1.241 Good 18.8 2 PEN TiO ₂ 5 0.05 1.5 PP-PE 15 51 4.8 A A 1.238 Good 18.3 3 PET TiO ₂ 7 0.10 2.5 PP 8 76 3.5 A A 1.208 Good 22.2 4 PET BaSO ₄ 10 0.05 1.5 PP-PE 15 55 4.5 A A 1.235 Good 19.5 Comparative Example One PET TiO ₂ 5 0.10 2.5 PP 40 36 5.6 A A 1.282 Good 21.7 2 PEN BaSO ₄ 15 0.00 1.5 PP-PE 10 57 4.4 A A 1.224 Bad 18.4 3 PET TiO ₂ 5 0.05 0.0 PP-PE 20 38 8.9 A B 1.253 Good 21.3 4 PET TiO ₂ 10 0.05 10.0 PP 10 NA NA C B 1.221 Good 19.6 5 PET BaSO ₄ 5 2.00 2.0 PP-PE 5 71 4.3 A A 1.243 Bad 18.8 6 PET TiO ₂ 20 0.10 1.5 PP 10 48 4.7 B B 1.267 Good 18.5

Stabilizer: Tetrakis-3,5-di-t-butylhydroxyphenylpropanoyloxymethylmethane

Compatibilizer: Polypropylene-Maleic Anhydride Copolymer (PP-MA)

As can be seen from the above, according to the present invention, as a compatibilizer capable of improving their compatibility with polyester resins and polyolefin resins, it is light by adding a polymer having graft copolymer of maleic anhydride or succinic anhydride to polypropylene. A white porous polyester film having a papery texture can be obtained, and the processability in this process can be improved. Therefore, such a white porous polyester film can be used in various fields such as calendars, flyers, high-quality packaging, printing decorative paper, wallpaper as a substitute for paper.

Claims (10)

A white porous polyester film comprising a polyester resin and a polyolefin resin, comprising 0.5 to 5% by weight of a polypropylene succinic anhydride or maleic anhydride as a compatibilizer with respect to the total amount of the resin. White porous polyester film characterized by. The white porous polyester film of claim 1, wherein the film has a density of 1.1 to 1.25 gr / cm ³ . The method of claim 1, wherein the polyolefin resin has a content of 5 to 35% by weight based on the total amount of the resin, a melt index of 1 to 25gr / min, at least selected from ethylene, propylene, butene, pentene, hexene, octene White porous polyester film, characterized in that polymerized or copolymerized from at least one monomer. The method of claim 1, wherein the polyester resin is at least one selected from polyethylene terephthalate and polyethylene naphthalate, and comprises 0.005 to 0.5% by weight of the hindered phenolic compound and 0.01 to 10% by weight of inorganic fine particles White porous polyester film characterized by. 5. The white porous material of claim 4, wherein the inorganic fine particles have a diameter of 0.01 to 10 μm and are at least one compound selected from titanium dioxide, barium sulfate, calcium carbonate, silica, kaolin, talc, and zeolite. Polyester film. In the method for producing a white porous polyester film of a polyester resin and a polyolefin resin, Mixing a polyester resin and a polyolefin resin in a weight ratio of 95: 5 to 65:35 to form a first mixed resin, Adding a compatibilizer made of a polymer having maleic anhydride or succinic anhydride graft copolymerized to polypropylene to add 0.5 to 5 wt% of the first mixed resin to form a second mixed resin, Melting and extruding the second mixed resin to form a film sheet, and Biaxially stretching the film sheet comprising the step of producing a white porous polyester film. The method of claim 6, wherein the polyester resin comprises 0.005 to 0.5 wt% of a hindered phenolic compound and 0.01 to 10 wt% of inorganic fine particles. The method of claim 7, wherein the inorganic fine particles have a diameter of 0.01 to 10㎛, white porous, characterized in that at least one compound selected from titanium dioxide, barium sulfate, calcium carbonate, silica, kaolin, talc and zeolite Method for producing a polyester film. The white porous polyester according to claim 6, wherein in the forming of the film sheet, the average diameter of the polyolefin in the film sheet is 5 µm or less, and the average number of polyolefins in the film sheet 1000 µm ² is 50 or more. Method for producing a film. The method of claim 6, wherein the stretching in the biaxial stretching step comprises a stretching ratio of 2 to 5 times in both longitudinal and transverse directions.